This invention was developed to overcome a failure situation occuring between the engine and transmission in a military vehicle. In this particular vehicle the engine is connected to the bell shaped transmission housing by means of approximately 12 bolts extending through a peripheral flange on the transmission housing into blind tapped holes in the engine mating face. The engine block is formed of aluminum, and the transmission housing is formed of magnesium. In some cases the transmission housing broke off in the area of the flange. Inspection revealed that several of the bolts had become unthreaded from the tapped holes in the engine. It is suspected that when the bolts became unloosened during service the engine and transmission impacted back and forth, thereby exerting high mechanical shock loads on one another, leading to breakage of the transmission housing.
In an attempt to minimize or eliminate the bolt unloosening problem several expedients were tried, including the use of commercially available lock washers, spring friction grip washers,, and plastic inserts in the shank portions of the bolts (as used for example in special bolts trademark "lock-tite" ). In spite of the various attempted fixes the problem has persisted.
The present invention is directed to a washer-bolt assembly wherein the washer includes a special blade that can be moved from a non-obstructing position out of registry with the bolt head to a bolt-obstruct position engaged with a shoulder on the bolt. When the blade is thus engaged with the bolt head the bolt is positively prevented from rotating in the unthreaded direction.